The gigantic "Docking Logic" Article is done, and posted!
This has been one of our biggest robot research projects
yet, and after 7 months of hard work I can now present to
you the final report:

http://www.schursastrophotography.com/robotics/dockinglogic.
html

If someone in this group could please review this work, and
if they feel it can contribute to the robotics community,
Id very much appreciate that you post it as an article on
this robots.net home page. Thanks!

Well, we have finished the first five chapters and are on
the last one on our Docking Logic article. Weve covered
all the theory and graphics, and now the final chapter -
actual lab experiments testing the different technologies.

I hope to get the majority of the last chapter done by this
time next week.

Well, its been a whole month since I last posted, so here
is our progress on the Docking Logic Project. The
illustration graphics have been really killing me! So many
of them, in such detail. Anyway I only have about ten more
to go and ALL of the photos, movies, CAD graphics and yes
schematics for the giant article will be DONE.

Maybe after this weekend. Then I have to start writing the
mega article for you guys. we will cover beacons arrays,
beacon sources, charging teqniques, docking tricks and
methods, charging contacts and yes, even some of the
pitfalls of the commonly used teqniques.

Im looking at getting this whole thing done in about a
month I hope. But you know how that goes! ;)

We are on the last configuration to evaluate. So far, we
have fully tested the pros and cons of these types:

1. Dual hoops contacts
2. cylinder contacts
3. Flat plate on wall

The final configuration is a bit uncertain at this point,
but we are going to evaluate the method of simply driving
the robot onto a flat charge plate to replenish. Its not
as easy at it sounds! Using some sort conductive wheels is
not a good choice, you dont want to know what metal wheels
do to our wood floors in the house. Contacts that drag or
drop to the ground may be one solution. I dont like
dragging a set of contact brushes around the wood floor
either. Once we have fully evaluated this technique, all
the primary research is complete, and we will start the
huge write up on the "Docking Logic" subject.

If you have some novel way your robot docks to charge,
write us, we'd love to hear from you!

The programming, and hardware on the robot is finished for
our "Docking Logic" program, with the PICbot 5. We have a
huge amount of writing up to do on what has been learned so
far, a very in depth knowledge base for building a self
charging robot.

We are now left with evaluation of three different contact
configurations on the charging base:

Dual brass hoops

Antenna Post

Antenna flat plate

Here is the latest images, two new ones and a mpg movie of
the PIC bot V with the charging base we are now evaluating:

We are about halfway through the "Docking Logic" research
project after this weekend. It appears to be quite clear
at this point, it requires four sensors to successfully
dock your robot to a beacon localized charger, with a high
percentage of success. These sensors are:

1. An omni directional "system" which detects proximity to
the charger.

2. A precise becon homing sensor for final homing.

3. A frontal contact switch (could be bumper) to determine
physical contact with the charger. Could also be a
photocell.

4. A distance sensing device, such as IR ranging or sonar
that allows the robot to slow to a fractional speed when
very close to the charger to prevent it from "ramming" it
at full speed. (you wont beleive how important this is!)

We have finished the omni cone prox sensor docking, and we
are now replacing it with a multiple sensor ring around the
robot to give it a rough idea which direction the beacon is
when in the prox mode. The cone was fun, but this may be a
better solution. (?)

The design of the shape and technique of electrical
contacts is next, the two best contenders at this point are
frontal contact plates which contact a pair of hoops at any
angle, or whiskers that V into a post with contacts.

It must be remembered here that while any one can make a
robot dock with its charger, doing it successfully and in a
totally repeatalbe manner is lacking in the home robot
world at this point. (and Im not talking about the
horrendous helter skelter way robot vacs dock)

Our Docking Logic program is proceedng smoothly, and Ive
posted a few intermediate images of the project in progress
for you to see. The Picbot 5 robot has many faces during
this program, sometimes a huge omni sensor on its back,
other times a brass bladed beacon homing seonsor. Take a
look:

we made great progress this weekend on our Docking Logic
program. After determining the range and current
requirements for detection with a PNA4602 last week, we
next constructed an "Omni Cone" sensor. This is a
reflective cone which directs the light from all directions
to a single sensor below, and indicates the proximity to
the charging base, but not its direction.

It took five pages of hand written mathematics to define
how to make such a cone, and how to make one from a flat
piece of reflective material starting with a circle with a
pie shaped cutout.

Once the cone was made, we place the sensor under it at the
calculated distance, and confirmed its optical properties
by shining a laser horizontally at the inverted cone, and
the beam hit square on to the center of the sensor, from
all angles around the cone! Ill of coarse be posting this
set of calculations so you can make an omni sensor for your
robot as well in the final write up.

Next, we are working with directional sensors, and how to
home in with perfect accuracy on the charging beacon.

We are proceeding well with the first tests of the huge
Docking Logic program. The sensitivity of the PNA4602 is
startling to say the least! First we constructed an wave
form generator by programming a PIC 12F629 chip to go high
12uS, and low 12us. We used a 20mhz xtal for accuracy. WE
got 38.46mhz on the counter. That drives a 2n3904 which
drives the IR Led. The range was tested with various in
line current limiting resistors.

I first started with a standard 270 ohm, and had a range of
over 20 feet to make the PNA device active! So powerful
was the beam that the whole room lit up in IR and specular
sources were everywhere. Next we put a 50k pot in line,
and adjusted to set the distance the device would
activate. Much to our suprise, even at 50k, the PNA device
would slam on at about a foot. Phenomenal. For our
testing, we will now vary the power level to simulate the
effect of the beacon and how the robot will react to it at
its limits as well as when it is strong.

First of all, I want to key you in on what I found in
Phoenix where I work yesterday - the Mcdonalds Robosapien
Adventure meal! If your thing is those crazy humanoid
bipeds, the minuature one at Mcdonalds will surely excite
you.

Now, onto our project. We got our parts in the mail
last
night for our PicBot 5 program, Docking Logic. This will
be the most extensive, lavishly illustrated project yet in
this series, which have been recieved very well so far in
the world wide robotics community Im happy to say. HEre is
the outline for what we will be researching in "Docking
Logic":

1. The Beacon sensor will be the venerable but getting
obsolete Panasonic PNA4602, which runs at 38.5 khz. This
will not interfere with the IR Prox sensors, which are the
IS471 which run at a very different 8 khz. First we will
determine the range for various IR LED combinations at the
beacon source.

2. Next, we will evaluate using a omni cone reflector
on
the reciever and determine range and cone configuration.

3. Directional sensor design for homing on the
beacon.

4. Robot path tracking from current position to beacon
docking. I assume it will be some sort of zig zag S curve.

5. Beacon beam path aquisition. In other words, what
to
do when we encounter the docking beacon beam.

6. Charging base docking envelope. How accurately
can we
stop at the beacon in a position ready to charge?

7. STopping at the beacon/charging base in the exact
spot
without hitting it.

8. Electrical contacts for the determined docking
postion
envelope.

9. Error correction if docking is unsuccessful. In
other
words, adding some AI to the docking proceedure so the
robot can react more intelligently to mis docking issues.

10. Spin Nav docking. (looking for the beacon with a
photocell at the bottom of a tube)

11. Maybe docking with an omni sensor. (the Roomba
uses
this rather dubious method)

Note that I wont be covering the actual chargin proceedure
yet, thats the Picbot 6 project!

Anyway, its going to be the most exciting project yet,
and
should fill a huge gap in the knowledge base for online
tutorials on a subject that is often considered way too
difficult to implement in a home robot - self charging.